Recirculating toilet system for use in aircraft or the like

ABSTRACT

A recirculating toilet system for use in an aircraft or the like having at least one toilet with a valve-controlled drain line and a waste tank connected to the drain line having a flushing fluid therein. A valve-controlled flushing line is in fluid communication with both the tank and the toilet and at least one pump is provided for pumping the flushing fluid from the tank to the toilet. Means are provided for forming a vacuum in the tank so that when the toilet is flushed, waste products are sucked into the tank while the toilet is flushed with the flushing fluid.

United States Patent [1 1 [111 3,922,730 Kemper Dec. 2, 1975RECIRCULATING TOILET SYSTEM FOR 3,43l,563 3/1969 USE IN AIRCRAFT OR THELIKE [75] Inventor: James M. Kemper, Sherman Oaks, 33 35347 9/1974Calif. [73] Assignee: Monogram Industries, Inc., Santa i a g 'f g kMonica, Calif sszstant xammer uar evy Attorney, Agent, or FirmPoms,Smith, Lande & [22] Filed: Mar. 11, 1974 Glenny [21] Appl. No.: 449,619

[57] ABSTRACT [52] U S Cl 4/10 4/77 4/79, A recirculating toilet systemfor use in an aircraft or 2l0/167 the like having at least one toiletwith a valve. [51] Int. Cm /016 controlled drain line and a waste tankconnected to [58] Field of 12 17 76 the drain line having a flushingfluid therein. A valve- 4/79 89 90 6 S controlled flushing line is influid communication with 2 6 both the tank and the toilet and at leastone pump is provided for pumping the flushing fluid from the tank [56]References Cited to.the t0ilet.-Means are provided for forming a vac-UNITED STATES PATENTS uum in the tank so that when the toilet isflushed,

waste products are sucked into the tank while the toi- 2,749,558 6/1956Lent et al. 4/10 let is fl h d with the flu hi fl id 3,032,776 5/1962Obert ct al.... 4/131 X 3,079,612 3/196-3 Corliss 1. 4/10 11 Clalms, 3Drawms Flgures 33 Floor Line Signal L 5/ J Pu el 39 I 36 l 40 5o 5| I 57I 53 x& 34 53 P 52' 47 I 27 I2 US. Patent Dec. 2, 1975 Sheet 1 of 23,922,730

WOC

RECIRCULATING TOILET SYSTEM FOR USE IN AIRCRAFT OR THE LIKE BACKGROUNDOF THE INVENTION 1. Field of the Invention The invention relates to arecirculating toilet system; and, more particularly, to a recirculatingtoilet system for use in an aircraft or the like.

2. Description of the Prior Art Self-contained, recirculating toiletsystems are currently being used on large aircrafts. Such systemsgenerally comprise a plurality of substantially independent,recirculating toilet systems, each with its own filter and pump assemblyand storage tank.

Such prior art systems have varying disadvantages, a discussion of whichis presented in application Ser. No. 243,897, entitled MULTIPLERECIRCULATING TOILET, filed by James M. Kemper on Apr. 13, 1972, andcommonly assigned to Monogram Industries.

It is noted, however, that none of these prior art systems takeadvantage of the differential pressure created across the cabin of allrecent commercial aircraft. Further, the piping from the toilets to thesewage tank in such prior art systems are relatively high in insidediameter in order to permit the sewage from the toilets to flow bygravity to the sewage tank. This results in a considerable cost andweight problem. Finally, odors are present in these prior art systemsand the technology heretofore in this art did not remove all of theobjectionable odors from the lavatories in which the toilets areinstalled.

SUMMARY OF THE INVENTION It is an object of this invention to. providean improved recirculating toilet system for use in an aircraft or thelike.

It is a further object of this invention to provide such a recirculatingtoilet system which removes substantially all objectionable odors fromthe lavatory in which the toilets of such system are installed.

It is still another object of this invention to provide a recirculatingtoilet system for use on an aircraft which removes human waste productsfrom the toilets of such system without the use of gravity.

These and other objects are preferably accomplished by providing arecirculating toilet system having at least one toilet with avalve-controlled drain line and a waste tank connected to the drain linehaving a flushing fluid therein. A valve-controlled flushing line is influid communication with both the tank and the toilet and at least onepump is provided for pumping the flushing fluid from the tank to thetoilet. Means are provided for forming a vacuum in the tank so that,when the toilet is flushed, waste products are sucked into the tankwhile the toilet is flushed with the flushing fluid.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical, partlydiagrammatic, view of a recirculating toilet system in accordance withthe teach ings of my invention;

FIG. 2 is a view ofa portion of FIG. 1 showing a modification thereof;and

FIG. 3 is a block diagram, partly schematic, of the control system forthe toilet system of FIG. 1.

DESCRIPTION OF THE PRIOR ART Referring now to the drawing, arecirculating system 10 in accordance with the teachings of my inventionis shown. This system 10 is particularly designed to be used in anaircraft or the like and thus a portion of the skin or body shell 11 ofan airplane is shown. A plurality of substantially identical pumps 12through 14 (three being shown), are shown as connected in parallel to asingle flush manifold 15 which serves several, substantially identicaltoilet assemblies 16 through 20 (five being shown).

A push-button switch 21 is provided for each of the toilet assemblies 16through 20, which controls a flush valve 22 operatively engaging theflush manifold 15 to initiate a flushing cycle. A waste return line 23couples each toilet assembly 16 through 20 to a waste manifold 24leading to a single holding tank 25.

Pumps 12 through 14 are commonly connected to a pressure sensing line26, of a smaller internal diameter than flush manifold 15, which isadequate to signal pressure in the line 26 associated with the motor ofeach pump 12 through 14, respectively. Each of the toilet assemblies 16through 20 is coupled to flush manifold 15 through the solenoid flushvalve 22 which may beoperated by an electrical control assembly 31 whichwill be discussed further hereinbelow. A pressure switch 32 in pressuresensing line 26 applies an electrical signal output to the controlassembly 31.

Pumps 12 through 14 may be any suitable pumps, such as pumps having apumping capacity of twenty gallons per minute and as disclosed in myaforementioned copending application Ser. No. 243,897. Thus, asdisclosed in that application, in the event of failure of any of thepumps 12 through 14, a failure warning indicator panel 33 may beprovided at a remote location and operatively connected to controlassembly 31 so that repair crews may be alerted to repair or replace thefailed pump. Conventional one-way check valves 27 through 29 may beassociated with each pump 12 through 14.

As particularly contemplated within the present invention, waste removalmeans are provided for removing waste from toilet assemblies 16 through20. In the exemplary embodiment, such waste removal means, indicatedgenerally at 34, includes the inner pressurized area 35 of the aircraftitself which may be referred to as the cabin of the aircraft. Thus, allpresent day commercial aircraft ordinarily fly at about 12,000 feet ormore and have a pressurized cabin which is higher in pressure than thepressure outside of the aircraft. Thus, the cabin may be kept at a sealevel pressure, such as 18 inches of mercury. A vacuum regulator may beused to automatically create a vacuum within tank 25. That is, inaddition to area 35, waste removal means 34 includes a vacuum line 36extending to an opening 37 formed in the shell 11 of the aircraft and incommunication with an opening 38 at generally the top of holding tank25. A vacuum regulator 39 is operatively disposed in line 36 betweenopenings 37 and 38 to maintain the interior 44 of tank 25 under vacuum.

It can be seen that waste manifold 24 is in fluid communication withboth waste return lines 23 from t'oilet assemblies 16 through 20 and aholding tank line 40 leading into holding tank 25 at substantially theupper end thereof.

It can also be seen that a solenoid drain valve 30 is operativelyconnected to a diaphragm actuated flapper seal 41 adapted to selectivelyopen and close the discharge portion 42 of the bowl 43 of each toiletassembly 16 through 20.

In this manner, the interior 44 of holding tank 25 is kept under vacuum.A drain or pumpout line 45 may be in fluid communication with a portionof holding tank 25 substantially above the lowermost end thereof alongline 47 but below generally the midpoint thereof. This pumpout line 45extends to a port 46 in shell 11 so that waste solids may be removed,when desired, from the interior 44 of tank 25.

The interior 44 of tank 25 may also be diagonally divided by a screen48, which may be of stainless steel, and have a mesh sufficient toprevent the passage therethrough of undesirable foreign matter, such asmetal particles or the like, from assemblies 16 through 20 so as toprevent damage to pumps 12 through 14. It can be seen in FIG. 1 that theinterior 44 of tank 25 includes a bottom section 49 below line 47. Asparticularly contemplated within the present invention, means areprovided for killing any bacteria in the fluid returned from tank 25 andmaintaining this fluid clear. In the exemplary embodiment, such means,indicated generally at 50, includes an injector 51 adapted to containtherein a predetermined quantity of chlorine 52 adapted to kill bacteriain the mixture of liquid waste and flushing fluid before the bacteriahas a chance to be absorbed by the flushing fluid. This keeps theflushing fluid clear when it settles in the bottom of tank 25. Thus,injector 51 may include an injection line 53 opening into the fluid intank 25 disposed above line 47. A suitable valve 53' controlled by asolenoid 52, may be provided in line 53 for controlling the injection ofchlorine from injector 51 into tank 25. Solenoid 52 may be operativelyconnected to control assembly 31 and controlled therefrom to release apredetermined amount, such as 30 ml, each time a toilet assembly isflushed as will be further discussed hereinbelow. A vent 50 may beprovided in injector 51. A drain line 54 extends from fluidcommunication with the lowermost portion of the bottom section 49 oftank 25 and to a pump manifold 55 in fluid communication with pumps 12through 14.

A surge tank 56 which is always kept under pressure by means of pumps 12through 14 is disposed in system in fluid communication with bothpressure sensing line 26 and a flush line 57 leading to manifold 15.This tank 56 may have a capacity of about 3 gallons if each pump 12through 14 is of a gallons per minute capacity. The outlets or dischargeportions 42 of bowls 43 are mounted within the floor 58 of the aircraft.

In operation, it can be seen that system 10 is designed to takeadvantage of the differential pressure across the cabin of the aircraftin which it is installed. The pressure within area 35 of the aircraft isgreater than the pressure outside of the aircraft. The sewage or holdingtank is thus exposed to the atmosphere outside of the aircraft by meansof vacuum line 36, regulator 39 regulating the vacuum formed in theinterior 44 of tank 25 as discussed hereinabove.

In a normal prior art waste disposal system, the waste products frombowls 43 must flow by gravity to tank 25. In this system 10, as eachflush valve is activated to open its respective seal 41, the combinationof the pressure in the aircraft cabin and the vacuum in the tank 25results in a tremendous suction taking place, which draws the wasteproducts within bowl 43 through discharge portion 43, into manifold 24and then into holding tank 25. This tremendous suction also sucks andthereby removes all undesirable odors in the lavatory in which toiletassemblies 16 through 20 are installed.

Since suction rather than gravity is used to empty bowls 43, the pipingfrom bowls 43 to tank 25 may be significantly less in internal diameterthan known prior art piping, as for example, piping having an internaldiameter of about 1 /2 inches compared to prior art piping having aninternal diameter of about 4 inches. This results in considerable costand weight savings. Also, when flush valves 30 close seals 41, sincetank 25 is in communication with the outside of the aircraft, noundesirable odors can enter the lavatory wherein assemblies 16 through20 are installed.

Tank 25 is initially charged with a suitable flushing fluid that is notsoluble in waste products, in this embodiment of the invention, aflushing fluid having a specific gravity at 20 C. higher than thespecific gravity of the waste products, i.e. higher than 1.0. Thus, asshown in FIG. 1, bottom section 49 of tank 25 holds the flushing fluidtherein and this fluid covers substantially the bottom of tank 25 to apreferable depth of about four inches.

Also, as shown, screen 48 filters out foreign matter onto one side ofthe interior 44 of tank 25 and the waste products (e.g., urine, humanwaste solids, and the flushing fluid) on the other. The mixture ofsolids, urine and flushing fluid settles so that the flushing fluid isbelow the urine due to its higher specific gravity. Of course, port 46permits tank 25 to be cleaned out when desired.

Thus, when a flush cycle is to be initiated at a toilet assembly, theappropriate push button switch 21 is activated signalling the controlassembly 31. As discussed in my co-pending application Ser. No. 243,897,one of the pumps 12 through 14 is then selected and power is applied toits motor. If operable, the selected pump will begin pumping. The fluidis pumped into line 26 and enters surge tank 56 which feeds fluidtherefrom through flush line 57 leading to flush manifold 15. The fluidpressure in manifold 15 will rise. The solenoid flush valve 22corresponding to the selected push button switch 21 is also energized toopen.

Thus, as the fluid pressure line 26, flush manifold 15 and flush line 57increases, pressure switch 32 is operated signalling to control assembly31 that the pressure has reached a predetermined minimum. The fluid isthen applied to the appropriate toilet assembly 16 through 20 throughthe open flush valve 22 and into a flushing pipe or line 59 opening intothe top of each bowl 43 to thereby flush the interior of the bowl.

The pressure sensing switch 32 operates the motor in the selected pumpto maintain the pressure in the flush manifold 15 below a preselectedmaximum.

Control assembly 31 may include a timing circuit therein to be discussedfurther hereinbelow to maintain the flush valve 22 open for a timedflushing interval. At the expiration of that interval, the flush valve22 is closed and the pump motor of the selected pump is de-energized.The operation of the various pumps if one or more fails to operate or ifa second button switch 21 is activated is described in detail in myco-pending application Ser. No. 243,897, the pertinent subject mattertherein being incorporated herein by reference.

Drain valves 30 are operatively connected to flushing line 59 and areopened upon the opening of flush valve 22 to thereby open flapper seals41. Since the interior 44 of tank 25 is under vacuum as heretoforedescribed, the waste products within bowls 43 are immediately suckedinto tank 25 to again initiate the discharge portion of system 10.

Although a flushing fluid having a specific gravity greater than 1.0 hasbeen disclosed, water, which has a specific gravity of 1.0, may be usedas the flushing medium. This is shown in FIG. 2 wherein like numeralsrefer to like parts of FIG. 1. Thus, tank 60 is identical to tank 25except that a screen 61 may be disposed in bottom section 49 and abovethe inlet of drain line 54 to screen the solids out of the mixture ofurine, water and solids.

If water is used as the flushing fluid, a predetermined amount ofchlorine is preferably injected along with the water since water willabsorb bacteria and oil will not.

That is if an oil is used as the heavier than water flushing fluid, itis well known that bacteria will not grow in oil. If water is used asthe flushing fluid, chlorine is injected along with the water to killany bacteria therein. The filtering medium will remove any solidmaterial and thus purify the urine in the urine-water mixture.

A control circuit for operating system of FIGS. 1 and 2 is shownschematically in FIG. 3. FIG. 3 has been generalized to cover a systemhaving N toilet assemblies and M pumps. This is indicated by applying tothe reference numerals of the several switches 21 a subscript 1 throughn. Similarly, the flush valves 22 are also suitably subscripted 1through n.

Connected to each push button 21, is a relatively long, interval timercircuit 140. The long timer circuit 140 is intended to be energized fora predetermined, adjustable time interval and provides a continousoutput during the timed interval. One output of the timer circuit 140 isapplied to energize the flush valve 22 and a second output is appliedthrough an or circuit 142, which applies its output to a counter 144 andto a second, relatively short, interval timer 146.

The or circuit 142 receives substantially similar inputs from each ofthe long interval timers 140 and provides a single output to theremaining elements of the control circuit 31.

The counter 144 may be a ring counter or any other conventional,addressing circuit which sequentially selects, in turn, M differentoutput lines, all of which are applied to a selection logic circuit 148which ultimately determines which of the M pumps 12, 13, 14 and 12m toenergize.

The output of the short interval timer 146 is applied on a first linethrough a normally closed set of switch contacts 132a to the selectionlogic circuit 148, and, on a second line through a second set ofnormally closed switch contacts 132b, to a medium interval timer 150.The output of the medium interval timer is also applied to the selectionlogic block 148.

The normally closed switch contacts 132a and 132b are directlycontrolled by the pressure switch 32 which, in this embodiment, isarranged to maintain switches 132a and 13212 in the closed configurationso long as the pressure detected is less than a preset magnitude. Whenthe prssure exceeds the limit, the two switches 132a and 13212 areopened, interrupting both circuits to the selection logic circuit 148.

As is well known in the design and construction of data processingequipment, the operation of the control circuit 31 may be represented bya series of logical equations which define the conditions under which anoutput is provided. Once these equations have been formulated, it isthen routine to design the appropriate structural elements that operatein accordance with these logical equations.

In operation, it will be seen that as a push button 21 is actuated, therelatively long timer is energized, which times the flush cycle. Acounting impulse is applied to the counter 144 to select one of thepumps. The selection is signalled on the appropriate output line to theselection logic block 148, which immediately energizes the selectedpump, injects chlorine from injector 51 into tank 25, and removesflushing fluid from tank 25 and pumps it through reservoir 56.

The relatively short interval timer 146 is energized for an intervalwhich is believed adequate to permit the selected pump to come to fullpressure in the line. The pressure switch 32 switch contacts 132a and1321; will be opened by the pressure increase and at the time that asignal output is provided by the short interval timer 146, the circuitwill be open.

If the pressure in the line is not adequate to open switch contacts132a, 132b, then a signal is applied by the timer 140 to the selectionlogic 148 and to the medium length timer 150. The selection logic 148then energizes a second motor. If the pressure in the line is stillinsufficient to open the switch contacts 132a, 132b, then the output ofthe medium interval timer 150, when applied to the selection logic 148,energizes the third motor of the group through the circuitry of theselection logic 148.

During a flush cycle, if the pressure drops sufficiently to reclose theswitch contacts 132a, 132b, a second pump is immediately energized, andif pressure is not restored within the interval timed by the secondtimer 150, a third pump is energized.

It is not believed essential to describe the detailed logic required toselect the appropriate failure warning lights in panel 33. It will beobvious to those skilled in the art that the circumstances dictating thelighting of the failure lamps can be easily expressed in logical termswhich can be simply mechanized.

The successive energization of more than one push button 21 will notaffect the state of the counter 144 so long as a pump is running.However, as soon as the latest flush cycle is concluded, and the pumpsdeenergized, the next energization of a push button 21 will advance thecounter 144.

It can be seen that I have described a recirculating toilet system whichis particularlay suited to take advantage of the pressurized cabin of anaircraft or the like. This system removes all odors from the lavatory inwhich the toilets of the system are installed when flush ing suchtoilets with a flushing fluid.

I claim as my invention 1. A recirculating toilet system for use in apressurized cabin of an aircraft or the like comprising:

at least one toilet assembly disposed in said cabin having avalve-controlled drain line;

a waste tank under vacuum operatively connected to said drain linehaving a pressure in its interior at a lesser pressure than the exteriorpressure at the toilet assembly;

vacuum controlling means associated with said tank for controlling thevacuum within the interior of the tank;

a valve-controlled flushing line communicating with both the interior ofsaid tank and said toilet assembly; and v at least one pump disposed insaid flushing line having an inlet in fluid communication with theinterior of said tank and an outlet in fluid communication with saidtoilet assembly.

2. The system of claim 1 wherein a pressurized surge tank having aportion of a flushing fluid therein is in selective fluid communicationwith the outlet of said pump.

3. The system of claim 2 including pressure response means associatedwith said pump and said surge tank adapted to respond to fluid pressurein said system to maintain a predetermined pressure at said toiletassembly.

4. The system of claim 1 wherein a plurality of toilet assemblies andpumps are provided, each of said pumps being controllable volume pumpsand means associated with each of said pumps adapted to respond to fluidpressure in the system to maintain a predetermined system pressure, saidpumps being connected to parallel to supply fluid to the toilet system,fluid pressure sensing means connected to the toilet system forproviding a first signal when sensed fluid pressure is less than apredetermined magnitude;

control means, connected to said pumps and said pressure sensing means,operable in response to applied first signals for energizing one of saidpumps for increasing the flow of fluid into the toilet system;

a switch at each of the toilet assemblies connected to said controlmeans, said control means being responsive to switch actuations forenergizing one of said pumps, said control means being further operablein response to said first signals for energizing the other of saidpumps.

5. In the system of claim 1 wherein a flushing fluid having a specificgravity greater than the specific gravity of water is disposed in saidwaste tank.

6. In the system of claim 1 wherein a predetermined amount of flushingfluid having a specific gravity lesser than the specific gravity ofwater is disposed in said waste tank.

7. In the system of claim 1 wherein said waste tank communicates withthe exterior of said aircraft and said vacuum controlling means isassociated with the communication between said waste tank and theexterior of said aircraft.

8. A method for flushing a toilet in a pressurized aircraft or the likewherein said toilet is installed in the interior of said aircraft andincludes a valve-controlled drain line, a waste tank in fluidcommunication with the drain line, a valve-controlled flushing linecommunicating with both the interior of said tank and said toilet and atleast one pump disposed in said flushing line having an inlet in fluidcommunication with the interior of said tank and an outlet in fluidcommunication with said toilet, the method which comprises the step of:

communicating the interior of said tank with the atmosphere outside ofsaid aircraft; controlling the communication between the interior ofsaid tank and the exterior of said aircraft to create a vacuum withinsaid tank at a pressure lesser than the exterior pressure at saidaircraft;

activating the valve of said flushing line to flush said toilet with aflushing fluid; and

sucking any waste products and flushing fluid in said toilet out of saidtoilet and into said tank due to the differential pressure between theexterior of said toilet and the interior of said tank thereby alsoremoving any undesirable odors in the portion of said aircraft wheresaid toilet is installed.

9. The method of claim 8 further including the step of maintaining apredetermined fluid pressure within said flushing line.

10. In the system of claim 8 including the step of initially placing apredetermined amount of flushing fluid having a specific gravity greaterthan the specific gravity of water in said waste tank.

11. In the system of claim 8 including the step of initially placing apredetermined amount of flushing fluid having a specific gravity lesserthan the specific gravity of water in said waste tank.

1. A recirculating toilet system for use in a pressurized cabin of anaircraft or the like comprising: at least one toilet assembly disposedin said cabin having a valve-controlled drain line; a waste tank undervacuum operatively connected to said drain line having a pressure in itsinterior at a lesser pressure than the exterior pressure at the toiletassembly; vacuum controlling means associated with said tank forcontrolling the vacuum within the interior of the tank; avalve-controlled flushing line communicating with both the interior ofsaid tank and said toilet assembly; and at least one pump disposed insaid flushing line having an inlet in fluid communication with theinterior of said tank and an outlet in fluid communication with saidtoilet assembly; and at least one pump disposed in said flushing linehaving an inlet in fluid communication with the interior of said tankand an outlet in fluid communication with said toilet assembly.
 2. Thesystem of claim 1 wherein a pressurized surge tank having a portion of aflushing fluid therein is in selective fluid communication with theoutlet of said pump.
 3. The system of claim 2 including pressureresponse means associated with said pump and said surge tank adapted torespond to fluid pressure in said system to maintain a predeterminedpressure at said toilet assembly.
 4. The system of claim 1 wherein aplurality of toilet assemblies and pumps are provided, each of saidpumps being controllable volume pumps and means associated with each ofsaid pumps adapted to respond to fluid pressure in the system tomaintain a predetermined system pressure, said pumps being connected toparallel to supply fluid to the toilet system, fluid pressure sensingmeans connected to the toilet system for providing a first signal whensensed fluid pressure is less than a predetermined magnitude; controlmeans, connected to said pumps and said pressure sensing means, operablein response to applied first signals for energizing one of said pumpsfor increasing the flow of fluid into the toilet system; a switch ateach of the toilet assemblies connected to said control means, saidcontrol means being responsive to switch actuations for energizing oneof said pumps, said control means being further operable in response tosaid first signals for energizing the other of said pumps.
 5. In thesystem of claim 1 wherein a flushing fluid having a specific gravitygreater than the specific gravity of water is disposed in said wastetank.
 6. In the system of claim 1 wherein a predetermined amount offlushing fluid Having a specific gravity lesser than the specificgravity of water is disposed in said waste tank.
 7. In the system ofclaim 1 wherein said waste tank communicates with the exterior of saidaircraft and said vacuum controlling means is associated with thecommunication between said waste tank and the exterior of said aircraft.8. A method for flushing a toilet in a pressurized aircraft or the likewherein said toilet is installed in the interior of said aircraft andincludes a valve-controlled drain line, a waste tank in fluidcommunication with the drain line, a valve-controlled flushing linecommunicating with both the interior of said tank and said toilet and atleast one pump disposed in said flushing line having an inlet in fluidcommunication with the interior of said tank and an outlet in fluidcommunication with said toilet, the method which comprises the step of:communicating the interior of said tank with the atmosphere outside ofsaid aircraft; controlling the communication between the interior ofsaid tank and the exterior of said aircraft to create a vacuum withinsaid tank at a pressure lesser than the exterior pressure at saidaircraft; activating the valve of said flushing line to flush saidtoilet with a flushing fluid; and sucking any waste products andflushing fluid in said toilet out of said toilet and into said tank dueto the differential pressure between the exterior of said toilet and theinterior of said tank thereby also removing any undesirable odors in theportion of said aircraft where said toilet is installed.
 9. The methodof claim 8 further including the step of maintaining a predeterminedfluid pressure within said flushing line.
 10. In the system of claim 8including the step of initially placing a predetermined amount offlushing fluid having a specific gravity greater than the specificgravity of water in said waste tank.
 11. In the system of claim 8including the step of initially placing a predetermined amount offlushing fluid having a specific gravity lesser than the specificgravity of water in said waste tank.